Operations on Matrices and Data Frames - English

Questions posted on ST Forums:

• assignment

  i am not able to do the second question of the assignment please help me with the command.

  12-13M 10-20S kinshuk02
  
  
  Answer last updated on: Aug. 17, 2021, 4:05 p.m.

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• Adding Multiple Data Frame

  Firstly, I performed rbind to add new data row.Then, the csv file is updated by doing write.csv operation.By running the R script file again, new column (X) exists in the dataframe and that makes number of columns of arguments do not match problem for further data frame addition.How to solve it?I also attached my code.captaincy=read.csv("CaptaincyData.csv")captaincy <- rbind(captaincy,data.frame(names="Dravid",Y=2008,played=25,won=8,lost=6,victory=0.32))write.csv(captaincy,"CaptaincyData.csv")In adding new column using cbind by running R script file repeatedly, new column exists. (in this case: just only new column exists)

  08-09M 40-50S EKW
  
  
  Answer last updated on: Feb. 6, 2021, 2:04 p.m.

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• File captaincy is not opening

  source('C:/Users/Joohi/Desktop/My Project/Matrices/myMatrix.R', echo=TRUE)> # Clear R workspace> rm(list = ls() ) > # Declare a variable to read and store the data frame > captaincy = read.csv("CaptaincyData.csv")Error in file(file, "rt") : cannot open the connectionIn addition: Warning message:In file(file, "rt") :  cannot open file 'CaptaincyData.csv': No such file or directory> # Clear R workspace> rm(list = ls() ) > > # Declare a variable to read and store the data frame > captaincy = read.csv("CaptaincyData.csv")Error in file(file, "rt") : cannot open the connectionIn addition: Warning message:In file(file, "rt") :  cannot open file 'CaptaincyData.csv': No such file or directory> > # View the stored data frame > View(captaincy)Error in View : object 'captaincy' not found> CaptaincyData <- read.csv("C:/Users/Joohi/Desktop/My Project/Matrices/CaptaincyData.csv")>   View(CaptaincyData)> # Clear R workspace> rm(list = ls() ) > > # Declare a variable to read and store the data frame > captaincy = read.csv("CaptaincyData.csv")Error in file(file, "rt") : cannot open the connectionIn addition: Warning message:In file(file, "rt") :  cannot open file 'CaptaincyData.csv': No such file or directory> > # View the stored data frame > View(captaincy)Error in View : object 'captaincy' not found> # Clear R workspace> rm(list = ls() ) > > # Declare a variable to read and store the data frame > captaincy = read.csv("CaptaincyData.csv")Error in file(file, "rt") : cannot open the connectionIn addition: Warning message:In file(file, "rt") :  cannot open file 'CaptaincyData.csv': No such file or directory> > # View the stored data frame > View(captaincy)Error in View : object 'captaincy' not found> # Declare a variable to read and store the data frame > captaincy = read.csv("CaptaincyData.csv")Error in file(file, "rt") : cannot open the connectionIn addition: Warning message:In file(file, "rt") :  cannot open file 'CaptaincyData.csv': No such file or directory> > # View the stored data frame > View(captaincy)Error in View : object 'captaincy' not found> 

  01-02M 10-20S Joohi
  
  
  Answer last updated on: Dec. 14, 2020, 1:38 p.m.

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• Remove of specific row

  Sir I like to ask what is the command for removing the added row in the matrixes as by mistake add command two times because of which I made the entry of Kohli two times. As it is out of the topic but sir I am facing this problems. Kindly guide me to know the command for removable of specific row.

  09-10M 40-50S manishakdey@gmail.com
  
  
  Answer last updated on: June 28, 2020, 1:36 a.m.

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• Finding sum of all elements in matrixA using inbuilt functions

  startTime <- Sys.time() totalsum <- 0 for (i in 1:3) {  for (j in 1:3) {    totalsum <- totalsum+matrixA[i,j]     } } print(totalsum)[1] 237endTime <- Sys.time()endTime- startTimeTime difference of 0.008000851 secs startTime <- Sys.time() sum(matrixA)[1] 237 endTime <- Sys.time() endTime- startTimeTime difference of 0 secsSir the above time difference is ok

  08-09M 20-30S Alamu
  
  
  Answer last updated on: May 17, 2020, 12:26 a.m.

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• Creating New Row

  inputcaptaincy <- rbind(captaincy,                    data.frame(names= "Kohli",                                        y=2016,                                        played=30,                                        won=20,                                        lost=9,                                        victory=20/30                                        )                   )View(captaincy)OutputError in match.names(clabs, names(xi)) : names do not match previous names

  10-11M 10-20S kalaibalakannan@gmail.com
  
  
  Answer last updated on: April 29, 2020, 1:54 p.m.

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• Operations on Matrices and Data Frames

       [,1] [,2][1,]    9   10[2,]   11   12[3,]   13   14[4,]   15   16           valuesC[1,]  9 10      17[2,] 11 12      18[3,] 13 14      19[4,] 15 16      20  how to change the row header to 1, 2, 3. in the above output row header is not appearing for two columns. kindly guide.

  11-12M 40-50S angaiaruvi@gmail.com
  
  
  Answer last updated on: April 28, 2020, 2 p.m.

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• Usage of rbind function

  1. Can a row be inserted in the middle of data frame using rbind function?2. Can multiple rows be inserted at once using rbind function in data frame?3. Can a data be inserted at once in  multiple data frames using rbind function? 

  10-11M 10-20S annieahuja89@gmail.com
  
  
  Answer last updated on: April 2, 2020, 11:32 p.m.

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• Regarding Matrix Operations

  Apart from binding rows and cols using rbind and cbind , it would be more helpful, if the video suggests edit and delete operations on a matrix.

  11-12M 50-60S sureshk1704@gmail.com
  
  
  Answer last updated on: Oct. 12, 2019, 4:23 p.m.

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